Survival of agricultural cultivates during its development, in the face of multiple pathogenic agents attacking them, is due principally to the natural existence of biological control. Several microorganisms capable of antagonizing the effect of other phytopathogenic microorganisms give this control.
Development and application of this natural potential is becoming more and more important as man has become able to participate and improve it and, will almost certainly have a big impact in agriculture in the near future, since the use of biological control agents in the country is an important factor in reducing chemical pesticides and therefore pollution, caused thereby.
In general, the microorganisms used in biological control are originated from isolates carried out from soil. However, not all isolated microorganisms present optimal characteristics for its use in biological control.
In this respect, the studies about behavior of these agents in different pH and weather condition and with several different microbial communities are very rare. However, some microorganisms have been accepted as biological control agents, as is the case of fungus belonging to the Trichoderma genus. As hyperparasites these active organisms have been proved extensively in field experiments, where it has been demonstrated that they can be effective as biological control agents against a very wide range of pathogens both air borne as soil borne, as it was described by Herrera-Estrella and Chet in 1998 (“Agricultural Biotechnology”, Arie Altman Ed. Marcel Dekker, Inc. New York, N.Y. USA pp. 263-282).
Likewise, several different factors have been identified as being involved in growth inhibition and/or pathogenic fungus destruction by Trichoderma, in which antibiotics and cell wall hydrolytic enzymes are found, besides to direct physical interaction that include winding over the host's hyphes and specialized structures formation of apprehensive type, as described in several references as above by Herrera-Estrella and Chet, or else, other references as that by Chet in 1987 (Ed. I. Chet, New York: Wiley & Sons. 137-160. b w), Dennis and Webster in 1971 (Trans. Brit. Mycol. Soc. 57: 41-48 and Trans. Brit. Mycol. Soc. 57: 25-39) and that of Elad, Chet and Henis in 1982 (Can. J. Microbiol. 28: 719-725).
Current Knowledge and techniques allow planning of use of improved strains of Trichoderma as an alternative in pathogenic fungus control in the country. However, up to date it has not been possible to carry out a largely effective and productive biological control, since no selection from suitable isolate or strain at country and weather conditions prevailing at the place where they are to be used has been carried out, so as according to the pathogen(s) agent(s)-object. The fact that no strain nor isolate can be considered of universal utility for control of all kinds of pathogens and all kinds of environmental conditions, makes that, despite the great development the use of these microorganisms have had in biological control, up to date it has not been possible to use them in the best manner, since in some cases the growth of the control agent is not enough, or basically it can not control all present pathogenic agents. Furthermore, when mixtures of strains or Trichoderma species are used to try to control different biologically pathogens, in some cases they inhibit each other creating a poorer biological control, instead of the improvement desired.
On the other hand, development of molecular genetic markers has opened doors for an intensive research and genetic characterization of many organisms such as bacteria, plants, fungus and insects. Such molecular markers allow collection and use of information of microorganisms of natural occurrence, in other words, carrying neutral phenotypicaly polymorphism within a population. The majority of the populations have relatively high frequency of such polymorphism, as they can be due to slight changes at DNA level such as base changes, insertions, deletions and translocations.
As a consequence thereof, it has been looked to abolish the inconveniences found in the use of the same Trichoderma strains for biological control of pathogenic fungus in the country, independently of environmental and weather conditions, through the development of a process that assisted by the use of molecular genetic markers, would allow the selection of Trichoderma strains having an optimal performance for biological control of certain specific pathogens of interest and at environmental conditions to which they will be subjected to at the country.